Complacent, self-complacent, self-satisfied, smug, priggish are comparable when they mean feeling or showing satisfaction especially in one’s own possessions, attainments, accomplishments, or virtues.
Complacent implies that a feeling of pleasure accompanies this satisfaction; it may suggest merely a sense of well-being that comes from having no complaint to make, or, at the other extreme, it may imply gloating over the success of something for which one is in some way or in some degree responsible.
Although complacent usually suggests an attitude toward oneself, it does not carry that implication so clearly that there is left no room for doubt.
For this reason self-complacent or self-satisfied is often preferred when an unequivocal or an unambiguous word is desired; both carry a strong implication either of a comparison made between oneself and others to the great disadvantage of the others or of a feeling that one can rise no higher.
Smug usually implies a habitual selfsatisfaction that arouses in some degree dislike or contempt; the term often implies both self-satisfaction and conscious respectability, and it may additionally connote narrowness or provinciality or a degree of selfrighteousness.
Priggish, like smug, is difficult to confine to any one sense or to any constant emphasis on certain implications; while it typically connotes either self-satisfaction, self-sufficiency, or self-righteousness, it usually also suggests either a more or less conscious assumption of one’s own superiority or an obvious effort to live up to what one considers one’s high principles or one’s high ideals.